Form not submitting when pressing enter

I have the following HTML/JS/jQuery Code. This code represents a login form that is presented modally to the user to allow them to login. The problem is, when I hit enter, the form does not seem to execute the "onsubmit" event. When I click the button as the bottom of the form (which has virtually the same code as the onsubmit event), it works perfectly. I am wondering if anyone can tell me why this form isn't submitting..? Any assistance would be appreciated.

jQuery Code to Show Login Modal:

showDivAndFocus('loginModal','loginaccount'); 

function showDivAndFocus(v,t){

    if (api)
        if (api.isOpened)
            api.close();

    api = $('#'+v).overlay({
        mask: {color: '#000000'}, 
        top:'0px',
        api: true,
        autoScrollToActive: false,
        autoScrollOffset: 0 
    }).load();

    document.getElementById(t).focus();
}

HTML Code

<div class="modal" id="loginModal">
    <h2>User Login</h2>
    <br />

    <form action="javascript:void(0);" onsubmit="return(doLogin());"  name="loginForm" id="loginForm">
        <table width="95%" cellpadding="4" cellspacing="4">
        <tr>
        <td class="regw" align="left"><b>Account Number:</b></td>
        <td class="regw" align="left"><input type="text" maxlength="10" size="10" name="loginaccount" id="loginaccount" /></td>
        </tr>

        <tr>
        <td class="regw" align="left"><b>Username:</b></td>
        <td class="regw" align="left"><input type="text" maxlength="20" size="20" name="loginusername" id="loginusername" /></td>
        </tr>

        <tr>
        <td class="regw" align="left"><b>Password:</b></td>
        <td class="regw" align="left"><input type="password" maxlength="20" size="20" name="loginpassword" id="loginpassword" /></td>
        </tr>  

        <tr>
        <td class="regw" align="left"><b>Remember Me:</b></td>
        <td class="regw" align="left"><input type="checkbox" name="loginremember" id="loginremember" /></td>
        </tr>  

        <tr><td colspan="2">
            <div>  
                <center>
                    <table><tr><td width="50" valign="middle">
                        <div id="loginLoading" style="height:24px;width:24px;"></div>   
                    </td><td>
                        <button onclick="doLogin();" type="button" class="ok">Submit</button>
                    </td><td>
                        <button onclick="api.close();" type="button" class="cancel">Cancel</button>
                    </td><td width="50">&nbsp;</td></tr></table>
                </center>
            </div>
        </td></tr> 
        </table>
    </form>
</div>

AJAX Call

function doLogin(){
    var ajax = getXmlObject();
    var f = getFormVariables();
    var url= '/login.php?f=' + encodeURIComponent(f);
    if (ajax.readyState == 4 || ajax.readyState == 0) {
        ajax.open("POST", url, true);
        ajax.onreadystatechange = function () {
            if (ajax.readyState == 4) {
                var a = ajax.responseText;
                if (a=="OK"){...} else {...}
            }
        };
        ajax.send(null);
      }
      return false;
 }

Solution

You have two choices:

Create an event handler for the enter button and add it to your bindings.
Use an <input type=submit> in the form somewhere, which is what gets the automatic Enter Key behavior you're after.